Preparing Your Garden for Fall

Warm Soil and Waning Sun

A garden designed by Pat Brodie.

Late-Summer Plantings

Every year, the gardening gurus and their ilk tell us this is the best season of all to plant things. There is lots of evidence that they are right. Experience has shown that planting into the warm soil of late summer and fall provides many kinds of plants the environment they need to get well established before the cool-down. So, with that in mind, here are some tips on what to plant in the next month or so.

As soon as spring-flowering bulbs appear in the nurseries and home improvement centers, grab your favorites and get out the shovel or trowel. To ensure a successive bloom, plant some of these in the cutting garden: anemones (Anemone blanda, A. coronaria, and A.x fulgens), hybrid freesias, and ranunculus (Ranunculus asiatica). Others hardy in our area are: baboon flower (Babiana stricta varieties), Brodiaea and its relatives now known under the name Triteleia, daffodil (Narcissus species and varieties), amaryllis (Hippeastrum hybrids), corn lily (Ixia maculata), Rhodophiala bifida, Tritonia crocata, and Watsonia borbonica.

Quick-growing annuals that thrive in our mild winters can brighten up any garden. These will fill in empty corners or cover up those bulbs that won’t appear for several months. Sow seed or buy small seedlings of: calendula (Calendula officinalis), cottage pink (Dianthus plumarius is actually a perennial, but often grown as an annual), poor man’s orchid (Schizanthus pinnatus), snapdragon (Antirrhinum majus), lobelia (Lobelia erinus), stock (Matthiola incana), viola (Viola cornuta), Johnny-jump-up (V. tricolor), and pansy (V.wittrockiana).

Perhaps the plants that benefit most from fall planting are perennials. Although they may look a little sad at this time in their cycle, they will get a good head start if planted now. First the California natives: yarrow (Achillea millefolium), Western columbine (Aquilegia formosa), seaside daisy (Erigeron glaucus), buckwheat (Eriogonum several species), coral bells (Heuchera varieties), iris (Iris douglasii and I. innominata), hummingbird sage (Salvia spathacea), checkerbloom (Sidalcea species), blue-eyed grass (Sisyrinchium bellum), and many more. Check out the great selection at the Santa Barbara Botanic Garden plant sale on Saturday, October 13.

There are, of course, a huge number of other perennials from similar climates all around the world that benefit from establishing in the fall. Here are a few: butterfly weed (Asclepias tuberosa), aster (Aster many species and cultivars), basket-of-gold (Aurinia saxatilis), bellflower (Campanula many species and selections), Jupiter’s beard (Centranthus ruber), snow-in-summer (Cerastium tomentosum), coreopsis (Coreopsis many species and varieties), Gaura lindheimeri and selections, Corsican hellebore (Helleborus argutifolius), red-hot poker (Kniphofia uvaria cultivars), plume poppy (Macleaya cordata), catmint and catnip (Nepeta species and hybrids), geranium (Pelargonium selections), penstemon (Penstemon ), Russian sage (Perovskia species and hybrids), self-heal (Prunella vulgaris), sage (Salvia many species and selections), and meadow rue (Thalictrum both native and nonnative species).

There are a number of trees and shrubs that look their best this season, which you may wish to include in your garden. Here is a smattering, with trees first: strawberry tree (Arbutus unedo), angel’s trumpet (Brugmansia species and cultivars), Hong Kong orchid tree (Bauhinia blakeana), floss silk trees (Chorisia speciosa with pink flowers and C. insignis with white flowers), Natal coral tree (Erythrina humeana), giant thevetia (Thevetia thevetioides), and princess flower (Tibouchina urvilleana). And now for the shrubs: blue hibiscus (Alyogyne huegelii), Camellia sasanqua and its many selections, Euryops pectinata (both gray- and green-leaved forms), oleander (Nerium oleander), Cape plumbago (Plumbago auriculata), and myriad species and hybrid roses.

Feed the Flora with Mulch

Fall is a great time to contemplate and prepare for the coming seasons. Plants planted now will establish a healthy root system much faster than those introduced to the garden in the spring. The soil is at its warmest and most active as summer wanes. All those creatures that make for healthy soil and plants-from microbes to earthworms-are present in teeming hordes right now. So it’s not only a great time to plant, it’s a great time to increase the health of the soil itself.

Add organic matter and they will come. The breakdown of plant parts is the basis of good soil fertility and the health of the complex web of organisms that inhabit it. In nature, leaves, twigs, flowers, fruits, even whole trees and shrubs fall to the ground when their season is over. They have captured energy from the sun and used it to convert gaseous carbon dioxide and liquid water into cellulose and simpler carbohydrates. They have also taken nutrients such as nitrogen, phosphorus, and potassium from the soil along with other trace mineral necessities like manganese and iron to complete their life cycle. All these essential elements can and will be returned to the soil through the actions of myriad “lower” organisms. The amazing reward for plants (and us) from these lowly inhabitants is that they don’t use it all for themselves; they take a little and leave a lot behind. As they recycle the organic bits that once were part of a rose or a redwood, they make the elements available again to a new generation of plants.

As gardeners, we can contribute to or confound these natural processes. When we rake or blow our landscapes bare of leaves and petals, we deprive the recyclers of their nutrient supply. We starve them into extinction and leave the soil itself incapable of supporting plant life. But if we leave the autumn leaves, if we compost the lawn clippings and other garden trimmings and use that compost to sustain new plantings, if we mulch our gardens with our own or other reclaimed garden waste, we feed the cycle again.

Fall is a great time to make compost. As you clean up the old leaves of irises, agapanthuses, gladioli and deadhead roses, alstroemerias, and hydrangeas, put this harvest to work for you. As the runner beans and cucumbers give up their final crop, their vines will contribute their carbon and nitrogen stores to the compost bin and feed the many decomposers. Through their actions, these tiny creatures chemically alter the nitrogen and other nutrients once locked up in plant tissues and make them available again to plants.

The cast of characters is large-from multitudes of microscopic bacteria to mysterious fungi with networks of hyphae that can pervade the entire compost bin from one initial spore. There are insects whose mandibles physically break down the fibrous tissue and earthworms that engorge the whole lot and disgorge it again in a supremely refined form, the “gold” in the dross. Each is, of course, an opportunist, with a tiny agenda of its own. They already exist in the air, on surfaces of soil, and roots of plants we gather, hiding in the corners that we didn’t reach with our rakes and brooms, so there is no need to capture and tame them. Assemble the pile of ingredients and they will move right in to colonize and capitalize on the bounty. Your reward is the compost. It is rich in soluble forms of nitrogen, myriad fungi that can form beneficial relationships with plant roots, and other beneficial organisms such as bacteria and nematodes that defend against pathogens and pests.

Compost is not the only way to introduce this bevy of beneficials. Organic materials placed on top of the soil as mulch will also attract many other denizens eager to attack and use this source of nutrition. They, too, use but little and leave behind a ready source and more accessible source of plant nutrition.

Perhaps you have noticed the lack of the word fertilizer in this discourse. In my (old) dictionary, fertilizer is defined as “substance used to fertilize soil; esp.: one chemically prepared that supplies nutrients :” If you harness the natural forces of organic matter recycling, you will have no need of “chemical” fertilizers. Consistently maintained mulch will contribute more than enough nutrients to your plants. It may take some time to restore adequate levels to severely depleted soil, but mulching combined with additions of compost when preparing soil for planting can restore soil health in a remarkably short time. And healthy soil means healthy plants that are able to resist disease and pest outbreak.

Keep the Summer Heat in a Homemade Greenhouse

It’s never too hot and it’s never too cold here along the South Coast. That means we can grow an astonishing array of plants year ’round without much effort. Toss out some seeds, stick in some seedling plants, and we’re good to go. Why, then, would we bother to build greenhouses or use some of the techniques to which folks in colder climes have to resort? Pushing the limits is what it is all about.

Gathering just a little more heat for those heat-loving plants and concentrating it right where it will do the most good is the underlying premise for these kinds of structures.

Your pet orchid from the tropics may need a rest after blooming, or you may want to try your hand at growing tomatoes in winter. Either of these projects will require some sort of greenhouse large enough to accommodate the plants and have some air circulation to keep them healthy. But if you just want to get a jump on the next season by starting seeds early or if you want to harvest succulent greens and other veggies through winter, a simple cold frame may be the structure for you.

Cold frames are low boxes with a transparent top. A typical construction will utilize a discarded window frame as the top and perhaps even the hinges on which it might have hung. The sides are often wooden, but elegance is not required, so scrap plywood is fine. One quick and dirty way to make a cold frame is to throw down four (or more) bales of straw and find a bit of glass or plastic to cover the top. Many refinements are possible, of course. One major one, if you are building with wood, is to have the top edge of the sides of the box cut on a slant. The exact angle isn’t too critical, but in the winter when the sun is low in the sky, an angled glass top will capture more solar energy and light than a flat one. Depending on circumstances (more to follow), you will want to prop open the top on warm sunny days, so hinges are very nice. Then some sort of prop to hold it open can be devised as well. If you really want to go all out, a cold frame crafted with superior materials and care could become a tasteful addition to any landscape.

Starting seeds in flats or other low containers is a snap with a cold frame. Even though it isn’t sealed or insulated, the air inside will be a few degrees warmer and a little more humid than outside. Seeds will sprout sooner and require less vigilance to keep them moist. Once seeds have germinated, do remember to check them and crack open the top to allow for air circulation. Inside temperatures can climb quickly to fairly high levels (think of your locked car with its windows rolled up) and plants can begin to steam early in the day. As days grow warmer, opening the top fully may be needed. When plants approach optimal size for transplanting, opening the cold frame for longer and longer periods will acclimate them to the environment they will encounter outside the box.

Gourmet-quality salad ingredients can also thrive in a cold frame through the cool winter months. There are plenty of winter greens that do just fine outside here, but if you want a perfect head of butter lettuce and a handful of tasty and colorful violas and nasturtiums for that New Year’s dinner salad, a cold frame might be for you. Cold slows down all the processes involved in plant growth, so keeping them a little warmer will lead to earlier harvests. Sow seeds or transplant young seedlings directly into soil inside the cold frame. Again, monitoring temperatures on sunny days is prudent.

Another good use for cold frames is as a temporary refuge for tender potted plants during those infrequent frost alerts. While cold frames are not sealed and insulated, they can elevate the temperature inside the extra few degrees necessary to prevent damage. Of course, a straw bale version will actually provide insulation and even better protection. We may not live in Montana, but cold frames can aid and extend our season, too.


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